The present invention relates to a hydraulic swing motor which generates a reciprocating swing motion by means of a hydraulic fluid. More specifically, it relates to an improvement of the brake mechanism which is used to lessen the shock occurring at the stroke end by applying a braking force towards the end of the stroke.
Generally speaking, when the load on a hydraulic swing motor is increased, the increased inertia will make it difficult to reduce the speed of operation or to stop the movement. As the stroke nears its end, therefore, there will be a considerable shock, with the danger of damage to the mechanical members.
In the past several countermeasures have been adopted to produce a cushioning effect. Namely, the discharge port has been separated into several units or made into a slender opening elongated circumferentially near the end of th stroke so as to be closed gradually by the vane before the swing stroke nears its end and so to produce a cushioning effect due to a decrease in the fluid discharge rate.
Even though such means as the above may work satifactorily when the load on the hydraulic motor is relatively small, they suffer from the defect that as the load is increased a fairly extensive cushion stroke zone becomes necessary to lower the stroke speed or to stop it smoothly by applying an adequate braking force while preventing abnormal pressure rises, and also that the effective stroke length or effective work is reduced after deducting the said cushion stroke sector.